Polyphenol, Ascorbic Acid and Total Carotenoid Contents in ...

MÉLO, E. A. et al.Polyphenol, Ascorbic Acid and TotalCarotenoid Contents in Common Fruitsand Vegetables1. INTRODUCTIONFruits and vegetables not only provide a small part ofthe daily caloric intake of our diet, but also certain substanceswith antioxidant capacity such as vitamin C (ascorbic acid),carotenoids and polyphenols. Recently there has beenincreasing interest in the protective biochemical function ofthese phytochemicals in the prevention of oxidative damageto an organism. In the past few years, an increasing numberof epidemiological studies have shown an inverse correlationbetween the consumption of fruit and vegetables and theincidence of degenerative diseases (AMES et al., 1993; RICE-EVANS & MILLER, 1995). In the past few years there has beenincreasing interest in determining relevant dietary sources ofantioxidant compounds (ŠKERGET et al., 2005; SCALZO et al.,2005; CIEŚLIK et al., 2006).Interest in food composition has broadened to includebioactive components as well as nutrients. Therefore, the termfunctional food was coined to describe foods that, as normaldietary constituents, can provide sufficient amounts of bioactivecomponents to prevent or delay chronic disease and therebyimprove public health (MILNER, 2002). Data on the levels ofbioactive components in foods are needed so that researchmay accurately assess their dietary intake, investigate theirphysiological functions, and determine their relationships tohealth and disease (PENNIGTON, 2002).Different plants have different contents of phytochemicalswith different structures and thus offer different protectivemechanisms at different levels. Moreover, the phytochemicalcontents of freshly harvested edible plants vary, and thesevariations result from an interplay of a number of factors, chieflygenetics, sunlight, reliable rainfall, topography, soils, location,season, soil fertilisation and maturity (HARRIS, 1977). Studiesrelating to the bioactive phytochemical contents of Brazilianfruits and vegetables have only been sparsely reported andtherefore it is important to know the total amount of thesephytochemicals in the diet. The current study was undertaken todetermine the concentration of polyphenols, total carotenoidsand ascorbic acid in some common fruits and vegetablesavailable on the market in Recife-PE Brazil.2.1 Fruits and vegetables2. MATERIAL AND METHODSFifteen different fruits and fifteen different vegetableswere selected on the basis of their high availability on the marketaccording to the Pernambuco Central Market (CEAGEPE).Samples of ripe fruits and vegetables (approximately 300 geach) were purchased fresh from a local supermarket in Recife-PE-Brazil in three different months, when they were mostavailable, during the year of 2004. The fruits and vegetablescomprised watermelon (Citrullus vulgaris), melon “Japonês”(Cucumis melo L. var. inodorus), melon “Espanhol” (Cucumismelo L. var. reticulares), guava (Psidium guajava), papaya cv.“Formosa” (Carica papaya), papaya cv. Hawaii (Carica papaya),cashew-apple (Anacardium occidentale L.), pineapple cv.“Perola” (Ananas comosus L.), orange (Citrus sinensis), bananacv. “comprida” (Musa paradisiaca L.), banana cv. “Pacovan”(Musa corniculata L.), mango cv. “rosa” (Mangifera indica),mango cv. “espada” (Mangifera indica), white onion (Alliumcepa), red onion (Allium cepa), green grape var. Itália (Vitis sp),red grape var. Patrícia (Vitis sp), spinach (Spinacia oleracea),lettuce cv. “crespa” (Lactuca sativa), lettuce cv. “lisa” (Lactucasativa), collard greens (Brassica oleracea var. acephala), greencabbage (Brassica oleracea var. capitata), red cabbage (Brassicaoleracea), potato (Solanum tuberosum), carrot (Daucuscarota), cauliflower (Brassica oleracea var. botrytis L.), tomato(Lycopersicon esculentum), green bean (Phaseolus vulgaris var.),cucumber (Cucumis sativus L.) and chayote (Sechium edule).2.2 Sample preparationAfter purchase, each fruit and vegetable was washedunder running tap water and the edible portion homogenizedusing a food processor. Immediately after homogenisation, 2 to5g aliquots for fruit pulps or 2 to 10g aliquots for vegetable pulpswere submitted to the determination of ascorbic acid using the2,6-dichlorophenol indophenol titrimetric method (AOAC, 1990).The remaining pulp was kept frozen at –18°C in polyethylenecontainers for the subsequent analytical determinations, whichwere carried out in the following 4 days.2.3 Determination of total phenolic contentsFruit and vegetable pulps (10 g) were submitted toextraction with 80% aqueous methanol (30 mL) for 20 min withagitation (magnetic stirrer) at room temperature (28 ± 2°C),and the mixture then filtered. The residue was mixed withanother 30 mL of 80% aqueous methanol and the extractionprocess repeated twice. The resultant methanolic extracts werecombined and completed to a final volume of 100 mL. Thetotal phenolics content was measured spectrophotometricallyat 725 nm using the Folin–Ciocalteu reagent (WETTASINGHE& SHAHIDI, 1999). The results were expressed as catechinequivalents (mg 100g –1 ) of the fresh weight.2.4 Determination of total proanthocyanidincontents (condensed tannins)Fruit and vegetable pulps (20 g) were submitted toextraction with 80% aqueous acetone (30 mL) for 20 min withagitation (magnetic stirrer) at room temperature (28 ± 2°C),and the mixture then filtered. The residue was mixed with30 mL of 80% aqueous acetone and the extraction processrepeated twice. The resultant extracts were combined andcompleted to a final volume of 100 mL. The proanthocyanidinscontent was measured according to the vanillin–HCl method(TIITTO-JULKUNEN, 1985). Briefly, 0.1–0.5 mL of extract wasintroduced into test tubes and covered with aluminium foil.Three millilitres of 4% vanillin (w/v) in methanol were added,and the tubes shaken vigorously. 1.5 mL of concentrated HClBraz. J. Food Technol., v.9, n.2, p. 89-94, abr./jun. 2006 90

MÉLO, E. A. et al.Polyphenol, Ascorbic Acid and TotalCarotenoid Contents in Common Fruitsand VegetablesGORINSTEIN et al. (1999) reported lower contents fortotal phenolic compounds in guava (4.95 mg 100g –1 ) andpineapple smooth Cayene variety (1.34 mg 100g –1 ) as comparedto the samples analysed in the present study. According toSOMEYA et al. (2002), banana (Musa canvendish) imported fromthe Philippines had a total phenolic content of 232 mg 100g –1dry weight. CHU et al. (2002), determined the total phenoliccontents of 10 selected common vegetables and spinach hadthe highest amount (79.55 mg 100g –1 ), followed by yellowonion (68.90 mg 100g –1 ), cabbage (36.66 mg 100g –1 ), carrot(35.10 mg 100g –1 ), potato (23.31 mg 100g –1 ) and lettuce(22.55 mg 100g –1 ). VISON et al. (1998) reported that red onionhad a greater total phenolic content (116.00 mg 100g –1 ) thanyellow onion (69.60 mg 100g –1 ). In this study, the findings didnot show this trend.The total flavonol contents of the plant materialsinvestigated in this study varied from 0.32 to 76.83 mg 100g –1fresh weight. The collard greens had the significantly highestflavonol contents (P

MÉLO, E. A. et al.Polyphenol, Ascorbic Acid and TotalCarotenoid Contents in Common Fruitsand VegetablesCashew-apple had the significantly highest concentrationof ascorbic acid, followed by red cabbage and guava. Thelowest level was found in cucumber. SUNTORNSUK et al.(2002) reported similar concentrations of ascorbic acid in guavapurchased in markets in Thailand (80.1 mg 100g –1 ). The ascorbicacid contents of lettuce cv. “lisa”, white onion and tomatoare in agreement with those found by FRANKE et al. (2004),who reported values of 2.0 mg.100g –1 , 6.7 mg.100g –1 and10.0 mg.100g –1 , respectively.With regard to total carotenoids (Table 2), the highestconcentration was found in carrot (P

MÉLO, E. A. et al.Polyphenol, Ascorbic Acid and TotalCarotenoid Contents in Common Fruitsand VegetablesSPEEK, A.J. et al. Total carotenoid and b-carotene contents of Thaivegetables and the effect of processing. Food Chemistry, v. 27, p.245-257, 1988.SUNTORNSUK, L. et al. Quantitation of vitamin C content in herbal juiceusing direct titration. Journal of Pharmaceutical and BiomedicalAnalysis, v. 28, p. 849-855, 2002.TEE E-S.; LIM C-L. Carotenoid composition and content of Malaysianvegetables and fruits by the AOAC and HPLC methods. FoodChemistry, v. 41, p. 309-339, 1991.TIITTO-JULKUNEN, R. Phenolic constituents in the leaves of NorthernWillows: Methods for the analysis of certain phenolics. Journal ofAgricultural and Food Chemistry, v. 33, p. 213-217, 1985.VISION, J.A. et al. Phenol antioxidant quantity and quality in food:vegetables. Journal of Agricultural and Food Chemistry, v. 46,p. 3630-3634, 1998.WETTASINGHE, M.; SHAHIDI, F. Evening primrose meal: a sourceof natural antioxidants and scavenger of hydrogen peroxide andoxygen-derived free radicals. Journal of Agricultural and FoodChemistry, v. 47, p. 1801-1812, 1999.Braz. J. Food Technol., v.9, n.2, p. 89-94, abr./jun. 2006 94